Symantec Encryption Desktop Shred Free Space-Norton Security Disabled

Use of Symantec Encryption Desktop to shred the free space of Drive C has disabled Norton Security Deluxe twice recently. This required Norton Security to be installed again. This has occurred twice on two separate shredding processes in the past two weeks. Prior to this time shredding the free space of drive C was not a problem. Norton's continued in operation while the free space was shredded three times on each of the two occasions. This was the same procedure used in the past with now problems. Any ideas on what the problem is and how to prevent a future problem if the Symantec product is to be used for Drive C free space shredding?  I'm using Windows 7 Ultimate Service Pack 1 64 Bit, upgraded from Vista Ultimate, Intel Core 2 Quad CPU Q8300 2.5GHz RAM 8.0GB. Computer is an HP Pavilion a6750t .Thanks. 

                                                                                              Jerry

As you are using a Symantec product that seems to be causing a problem, you should post in the Symantec forums.

https://www.symantec.com/connect/

Your Norton product should not be able to be disabled by anything. Have you run a full system scan with your Norton product?  Check your Norton settings to make sure that Norton Product Tamper Protection is turned on in Administrative Settings.